Specific reciprocal chromosome translocations are very frequently found in human lymphomas and leukemias. These chromosomal abnormalities alter normal cellular genes leading to their deregulation. Chromosome translocations have been shown to play an important role in the pathogenesis of human leukemias and lymphomas by either activating cellular protooncogenes or by leading to the formation of chimeric genes capable of transforming hematopoietic cells. Erikson et al., Proc. Natl. Acad. Sci. U.S.A. 1983, 80, 519-523; Tsujimoto et al., Science 1984, 226, 1097-1099; Tsujimoto et al., Science 1984, 224, 1403-1406; Shtivelman et al., Nature 1985, 315, 35-354; Mellentin et al., Science 1989, 246, 379-382.
Translocations can lead to gene fusion resulting in a chimeric oncoprotein whose transforming activity is derived from both genes. The prototype of such events is the t(9;22) of chronic myelogenous leukemia (CML) which leads to a BCR-ABL fusion mRNA and protein (Shtivelman, supra). Translocations t(1;19), t(15;17), and t(6;9) are other examples of gene fusions, involving in the first two cases transcription factors (Nourse et al., Cell 1990, 60, 535-545; Kamps et al., Cell 1990, 60, 547-555; Kakizuka et al., Cell 1991, 66, 663-674; de The et al., Cell 1991, 66, 675-684; von Lindern et al., Mol. Cell. Biol. 1990, 10, 4016-4026).
The alternative molecular consequence of translocations is deregulation of protooncogenes by their juxtapositioning to an enhancer or promoter which is active in the type of cell from which the tumor arises. The immunoglobulin (Ig) and T cell receptor (TCR) enhancers participate in at least 15 different translocations associated with Burkitt lymphoma, chronic lymphocytic leukemia, follicular lymphoma, mantle cell lymphoma, and acute T or B cell leukemia. (Croce, CM, Cell 1987, 49, 155-156; Rabbitts, TH, Cell 1991, 67, 641-644; Solomon et al., Science 1991, 254, 1153-1160).
Chromosomal region 11q23 has been shown to be involved in different chromosomal translocations in human acute leukemias of different hematopoietic lineages. 11q23 chromosome abnormalities have been reported in acute lymphoblastic leukemia and in acute nonlymphoblastic leukemia (ANLL), most commonly of the M4 and M5A subtypes. Heim and Mitelman, Cancer Cytogenetics, Alan R. Liss, New York 1987. Chromosome 11 band q23 is frequently rearranged in acute lymphocytic (ALL), in acute myelomonocytic (AMMOL), acute monocytic (AMOL) and acute myeloid (AML) leukemias, mostly in reciprocal exchanges with various translocation partners. The t(4;11)(q21;q23), t(11;19) (q23;p13), and t(1;11)(p32;q23) are found in 10%, 2% and &lt;1% of ALL, respectively. Reciprocal translocation between 11q23 and chromosomal regions 9p22, 6q27, 1p21, 2p21, 10p11, 17q25 and 19p13 are found in 5-6% of AML. Heim and Mitelman, supra. In addition, interstitial deletions in 11q23 have been detected both in ALL and AML.
The same segment on chromosome 11 is apparently involved in the t(11;19)(q23;p13) and t(1;11)(p32;q23) translocations in ALL as well as in translocations with the chromosomal regions 9p21, 2p21 6q27, 17q25 and 19p13 associated with 5-6% of acute myelogenous leukemias (AML). Heim and Mitelman, Cancer Cytogenetics, Alan R. Liss, New York 1987. Reciprocal translocations between chromosome region 11q23 and chromosomal regions 9p22, 6q27, 1p21, 2p21, 10p11, 17p25 and 19p13 are found in 5-6% of ANLL.
In clinical terms, rearrangements of 11q23, in particular the t(4;11) chromosome translocation, have some distinct features. The patients are often quite young; t(4;11) accounts for the vast majority of cytogenetically abnormal ALLs in infants. In the majority of patients, the leukemic cells show both B-cell and myeloid marker (Stong et al. Blood 1986, 67, 391-397) and the disease is consequently considered "biphenotypic."
Among children, most patients with the t(4;11) abnormality are less than one year of age and have a poor prognosis. The leukemic cells have a CD10-/CD19+ early B cell precursor phenotype and most of them express a myeloid associated antigen (CD15); Pui et al., Blood 1991, 77, 440-447. Myelomonocytic and biphenotypic leukemias carrying the t(4;11) aberration have also been reported; Nagasaka et al., Blood 1983, 61, 1174-1181.
There remains an unmet need for identification of the breakpoint cluster region and the genes involved in chromosome 11 aberrations associated with acute leukemias in order to provide diagnostics and therapeutics for these diseases.